谁能给我讲讲英语知识啊?像:动词用法、人称用法、ing用法、过去式。还有...答:功能介绍 在功能上介乎主动词和助动词之间的一类结构,称为半助动词。常见的半助动词有be about to, be due to, be going to, be likely to, be meant to, be obliged to, be supposed to, be willing to, have to, seem to, be unable to, be unwilling to等。...情态助动词 情态助...